Co-occurring Disorders addresses a reality of substance use treatment: most clients have both a substance use disorder and a mental health condition. These conditions interact, each can worsen the other, and treating only one leaves the person at risk. Integrated, whole-person care produces better outcomes. This course covers what co-occurring disorders are, how common they are, how mental illness and substance use interact, the role of trauma, recognizing mental health symptoms, the principles of integrated treatment, and the front-line staff's role in supporting clients with complex needs. It connects to the behavioral health and trauma content elsewhere in the library. The throughline: people are whole, not a collection of separate problems. Recognizing and supporting both the substance use and the mental health needs — together — is how clients with co-occurring disorders recover.